CN101198564A - Modified sulfur and products comprising modified sulfur as binder - Google Patents

Abstract

The present invention provides modified sulfur prepared by mixing molten elemental sulfur with one or more olefinic sulfur modifiers, wherein at least 50% by weight of said olefinic sulfur modifier is 5-ethylene- 2-norbornene and/or 5-vinyl-2-norbornene, wherein the total amount of the olefinic sulfur modifier accounts for 0.1-20wt% of the sulfur weight. The present invention also provides products comprising such modified sulfur as a binder, prepared by mixing such modified sulfur, fillers and/or aggregates, and optionally elemental sulfur, and solidifying the mixture by cooling the mixture to a temperature below the melting temperature of sulfur.

Description

Modified sulfur and products comprising modified sulfur as binder

field of invention

The present invention provides modified sulfur and products comprising modified sulfur as a binder, prepared by mixing such modified sulfur, fillers and/or aggregates, and optionally elemental sulfur, and solidifying the mixture by cooling the mixture to a temperature below the melting temperature of sulfur.

Background of the invention

Conventional building materials such as mortar or concrete based on Portland cement have good durability under alkaline conditions. However, their acid resistance is poor. In acidic conditions, building materials with sulfur as a binder can be used, since these materials show very good stability in acidic conditions. However, the alkali resistance of sulfur bound products is poor, especially if compared to Portland cement products.

In sulfur-bonded materials such as sulfur cement or sulfur cement-aggregate composites, elemental sulfur is used as a binder. The sulfur used in such products is usually modified or plasticized to prevent allotropic transformation of the solid sulfur. Modified sulfur is typically prepared by reacting a portion of the sulfur with a sulfur modifier (also known as a sulfur plasticizer). A well-known class of sulfur modifiers are olefinic compounds copolymerized with sulfur. Known examples of such olefinic sulfur modifiers are dicyclopentadiene, limonene, styrene or naphthalene. See, e.g., B.R. Currell et al. "Plasticization of Sulfur" In: J.R. West (ed.), Proceedings of symposium "New Uses of Sulfur", Los Angeles, April 1974, Advances in Chemistry Series No. 140, Am. Chem. Soc, Washington , 1975, pp. 1-17.

Plasticized or modified sulfur can be used in the form of so-called concentrates, ie sulfur reacted with relatively large amounts of modifiers. To make sulfur bound products such as concrete, the concentrate is then mixed with other sulfur, fillers and aggregates and set at a temperature above the melting temperature of sulfur.

Summary of the invention

It has now been found that if sulfur modified with a specific amount of 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene is used as a binder, it is possible to obtain Both exhibit good durability of cement or cement-based building materials.

It is known to use ethylidene norbornene or 5-vinylnorbornene as sulfur modifier. In Research Disclosure no. 22924, 1983, ethylidene norbornene or 5-vinyl norbornene is mentioned as a sulfur plasticizer. In this example, the plasticized plastic was prepared by reacting elemental sulfur with 40-43% by weight of sulfur of an olefinic plasticizer as a blend including ethylidene norbornene and 5-vinyl norbornene. of sulfur. The resulting plasticized sulfur is a black glassy solid and is therefore not suitable for further processing into sulfur-bound products such as cement, mortar or concrete.

It has now been found that if the olefinic modifier used comprises at least 50% by weight of 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene and at any stage of the modified sulfur production process The total concentration of the olefinic modifier in the stage does not exceed 20wt% of the weight of the sulfur. If the obtained modified sulfur is used in a sulfur-bonded product, the sulfur-bonded product will be resistant to both acid and alkali.

Accordingly, the present invention relates to modified sulfur prepared by mixing molten elemental sulfur with one or more olefinic sulfur modifiers, wherein at least 50% by weight of said olefinic sulfur modifier is 5-ethylene- 2-norbornene and/or 5-vinyl-2-norbornene, wherein the total amount of the olefinic sulfur modifier accounts for 0.1-20 wt% of the weight of sulfur.

An advantage of the modified sulfur of the present invention is its high alkali resistance. Both the modified sulfur itself and the sulfur-bonded products prepared therefrom have surprisingly high alkali resistance.

Other advantages of the modified sulfur of the present invention compared to modified sulfur prepared with the most common sulfur modifier (i.e., dicyclopentadiene) are that 5-ethylidene-2-norbornene and 5-vinyl -2-norbornene is less toxic and more stable. Therefore, the processing of 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene into modified sulfur is simpler than that of dicyclopentadiene.

Another advantage of the modified sulfur of the present invention is its light color. Therefore, the sulfur-bonded products using the modified sulfur of the present invention are light in color and can be pigmented to a desired color.

In other aspects, the invention relates to a product comprising modified sulfur as a binder, prepared by mixing the above defined modified sulfur, fillers and/or aggregates, and optionally sulfur, and solidifying the resulting mixture by cooling the mixture to a temperature below the melting temperature of sulfur.

Detailed description of the invention

The modified sulfur of the present invention is prepared by mixing molten elemental sulfur with one or more olefinic sulfur modifiers. At least 50% by weight of said olefinic sulfur modifier mixed with said elemental sulfur is 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene.

The preparation of modified sulfur is known in the art. Molten elemental sulfur is mixed with one or more modifiers at a temperature above the melting temperature of sulfur (ie, above 120° C.) and below the boiling temperature of the modifiers to react a portion of the sulfur with the modifiers. Typically, the temperature is 120-150°C. The modified sulfur of the present invention can be prepared by mixing the sulfur and the modifier at any suitable temperature, preferably at 120-150°C, more preferably at 130-140°C.

In the preparation of the modified sulfur of the present invention, the elemental sulfur mixed with the modifier can be obtained from any source. Typically, the elemental sulfur will be elemental sulfur obtained as a by-product of desulfurization of crude oil, natural gas or ores. The elemental sulfur may include small amounts of impurities, typically in concentrations ranging from a few milligrams to a few grams per kilogram, such as mercaptans.

In the preparation method of the modified sulfur, the total amount of the olefinic sulfur modifier mixed with the sulfur accounts for 0.1-20 wt% of the weight of the sulfur. Smaller amounts, ie less than 0.1 wt%, will not provide the desired modifying effect of preventing allotropic transformation of solid sulfur. Higher amounts of olefinic sulfur modifiers, ie higher than 20 wt%, will give the modified sulfur undesired mechanical properties and an undesired dark colour. Furthermore, the modified sulfur thus obtained is no longer soluble in molten elemental sulfur and therefore cannot be used as a modified sulfur concentrate.

The advantage of using 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene instead of dicyclopentadiene as the most common olefinic modifier is that it is easier to process . During processing, the dicyclopentadiene dimer reverts to its volatile monomer and thus has to react with sulfur under reflux conditions. The reaction of 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene with sulfur can occur at a temperature below its boiling temperature, and thus the preparation of modified sulfur can be performed without modification under the reflux of the agent. Another advantage is that 5-ethylidene-2-norbornene and 5-vinyl-2-norbornene are much less toxic than dicyclopentadiene.

Preferably at least 80% by weight of the olefinic sulfur modifier mixed with molten sulfur is 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene, more preferably in the modification of the present invention In the production of sulfur, no olefinic modifiers other than 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene are used. Even more preferably, only 5-ethylidene-2-norbornene modifier is used.

The modified sulfur of the present invention is particularly suitable for use in products comprising modified sulfur as a binder. Examples of such sulfur-bound products are sulfur cement and sulfur cement-aggregate composites such as sulfur mortar, sulfur concrete or sulfur-filled asphalt.

Sulfur cements are known in the art and generally comprise modified sulfur (usually in an amount of at least 50 wt%) and fillers. Typical sulfur cement fillers are granular inorganic materials with an average particle size of 0.1 micron to 0.1 mm. Examples of such sulfur cement fillers are fly ash, limestone, quartz, iron oxides, alumina, titanium dioxide, graphite, gypsum, talc, mica, or combinations thereof. The filler content of sulfur cements can vary widely, but typically ranges from 5 to 50% by weight of the total weight of the cement.

The sulfur cement-aggregate composite referred to herein refers to a composite comprising both sulfur cement and aggregates. Examples of sulfur cement-aggregate composites are sulfur mortar, sulfur concrete and sulfur filled asphalt. Mortars consist of fine aggregates, typically particles of average diameter 0.1-5 mm, such as sand. Concrete consists of coarse aggregates, usually particles with an average diameter of 5-40 mm, such as gravel or rock. Sulfur-filled bitumen is bitumen, ie an aggregate, usually with a binder, containing filler and residual hydrocarbon components, where part of the binder has been replaced by sulfur, usually modified sulfur.

The sulfur-bonded products of the invention are prepared by mixing the modified sulfur of the invention with fillers and/or aggregates and optionally additional elemental sulfur. It should be understood that it depends on the desired product and on the amount of modifier-sulfur reaction product in the modified sulfur to be mixed with what components and in what amounts.

Preferably, the amount of olefinic modifier used in the preparation of the modified sulfur does not exceed 5% by weight of the weight of sulfur in the final product (ie sulfur bound product). The weight of sulfur in the sulfur-bonded product referred to herein refers to the total amount of sulfur used, i.e. the amount of sulfur mixed with the modifier in the preparation of the modified sulfur and optionally mixed with the modified sulfur in the preparation of the product. amount of sulfur mixed with filler/aggregate.

It has been found that the use of olefinic modifiers in an amount below 5% by weight of the amount of sulfur in the final product results in a stable product with good mechanical properties if it is exposed to alkaline or acidic conditions durable. An advantage of using relatively low amounts of olefinic modifiers is that the time required for setting is minimized. Preferably, the amount of the olefinic modifier is 0.1-4.0 wt%, more preferably 0.1-3.0 wt%, based on the total weight of sulfur in the product.

Preferably, so-called modified sulfur concentrates are used in the preparation of the sulfur-bound products according to the invention, i.e. modified sulfur which has been prepared with a modifier in an amount higher than that used in the sulfur-bound desired amount in the product. In this case, modified sulfur and elemental sulfur are mixed with fillers and/or aggregates in the preparation of sulfur-bonded products. An advantage of starting with a modified sulfur concentrate is that transportation costs can be limited if the modified sulfur is manufactured at a different location than the sulfur bound product.

Preferably, a modified sulfur concentrate prepared from sulfur mixed with 5-15 wt%, more preferably 7-12 wt%, of olefinic modifier based on the weight of sulfur is used.

Alternatively, modified sulfur may be used which already includes all the sulfur present in the resulting sulfur bound product. In this case it is preferred to use sulfur with 0.1-5.0 wt% olefinic modifier, more preferably 0.1-4.0 wt% olefinic modifier, even preferably 0.1-3.0 wt% olefinic modifier Modified sulfur prepared by mixing.

Preferably, the modified sulfur used to prepare the sulfur-bonded product is not olefinically modified with other than 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene modified by the agent. However, if the modified sulfur has been modified with 5-ethylidene-2-norbornene or a mixture of 5-vinyl-2-norbornene and other olefinic modifiers, the amount of other modifiers is preferred Up to 1% by weight of the total weight of sulfur in the sulfur bound product.

If one or more olefinic modifiers other than 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene are used in the preparation of the modified sulfur of the present invention, it can is any olefinic sulfur modifier known in the art, such as dicyclopentadiene, cyclopentadiene, styrene, dipentene, oligomers of dicyclopentadiene, or combinations of two or more thereof combination.

Example

The invention is further illustrated by the following non-limiting examples.

Example 1

The alkali resistance of unmodified and modified sulfur was determined.

Preparation of modified sulfur

The first modified sulfur (sample 1, according to the invention) was prepared as follows. Weigh the amount of elemental sulfur in a glass test tube. The test tube was placed in an oil bath at 135°C to melt the sulfur. A quantity (5% by weight based on the weight of sulfur) of 5-ethylidene-2-norbornene was added and the fluid was stirred for 3 hours. The tube was then removed from the oil bath and the fluid was poured into a cylindrical mold and allowed to solidify at room temperature.

The second modified sulfur (sample 2, according to the invention) was prepared as follows. Weigh the amount of elemental sulfur in a glass test tube. The tube was placed in an oil bath at 150°C to melt the sulfur. A quantity (10% by weight of sulfur) of 5-ethylidene-2-norbornene was added and the fluid was stirred for 1 hour. The tube was then removed from the oil bath and the fluid was poured into a cylindrical mold and allowed to solidify at room temperature.

Other modified sulfurs including 1.0, 2.5, 5.0 and 7.5 wt% of 5-ethylidene-2-norbornene were prepared by mixing sample 2 and additional elemental sulfur at 130°C (samples 3-6, all according to the invention). Each mixture was stirred at this temperature for 5 minutes and then poured into cylindrical molds and allowed to set at room temperature.

Other modified sulfur (sample 7, not according to the invention) was prepared as follows. Elemental sulfur and (by weight of sulfur) 10 wt% of a commercially available sulfur modifier STX ^™ (from STARcrete Technologies Inc.) were weighed in a test tube placed in an oil bath heated to 150°C. The mixture was stirred for 10 minutes. The tube was then removed from the oil bath and the fluid was poured into a cylindrical mold and allowed to solidify at room temperature.

A sample of unmodified sulfur (sample 8, not according to the invention) was prepared as follows. The test tube with elemental sulfur was placed in an oil bath heated to 150° C. for 10 minutes to melt the elemental sulfur with stirring. The molten sulfur is then poured into cylindrical molds and allowed to solidify at room temperature.

Alkali resistance

The alkali resistance of the modified sulfur prepared as above was determined by placing the cylinders in 5 M NaOH aqueous solution. The weight loss of the cylinder was measured after 15 and 20 days in 5M NaOH solution (wt% based on the initial weight of the sample). The results are shown in Table 1.

Table 1. Weight loss of modified sulfur after soaking in 5M NaOH

sample modifier Weight loss after 15 days (wt%) Weight loss after 20 days (wt%) Weight loss after 30 days (wt%) 1 5.0 wt% ENB ^a 2.2 2.7 2 10.0 wt% ENB ^a <1 3 1.0 wt% ^b of ENB ^a <1 4 2.5 wt% ^b of ENB ^a <1 5 5.0 wt% ^b of ENB ^a <1 6 7.0 wt% ^b of ENB ^a <1 7 10.0wt% STX ^™ 34 57 8 none 20 80 100

^a ENB: 5-ethylidene-2-norbornene

^b prepared from 10 wt% ENB sample (sample 2)

Example 2

Determination of alkali resistance of mortars prepared from unmodified and modified sulfur

Preparation of Sulfur Mortar

The sulfur mortar consisted of 50 wt% dry sand (Normsand), 30 wt% dry filler (quartz) and 20 wt% modified or unmodified sulfur, which was prepared by mixing these ingredients at 150°C until a homogeneous mixture was obtained preparation. The mixture was then poured into steel molds preheated to 150°C. Pressure (0.25-0.5 tons) was applied until droplets of sulfur were visible at the bottom of the mold. The mortar cylinder thus formed is then demoulded.

Three different mortars were prepared with different sulfur:

Mortar 1 - Unmodified elemental sulfur (not according to the invention). Dry sand (50wt%), dry quartz (30wt%) and elemental sulfur (20wt%) were mixed.

Mortar 2 - Sulfur modified with 11 wt% of STX ^™ (not according to the invention). Dry sand (50wt%), dry quartz (30wt%), elemental sulfur (18wt%) and STX ^™ modifier (2wt%) were mixed.

Mortar 3 - sulfur modified with 2.5 wt% of 5-ethylidene-2-norbornene (according to the invention). Mix dry sand (50wt%), dry quartz (30wt%), elemental sulfur (15wt%) and 5wt% modified sulfur, wherein the modified sulfur is composed of 10wt% 5-ethylene-2-nor Bornene preparation. The modified sulfur prepared from 10wt% 5-ethylidene-2-norbornene was prepared according to sample 2 in Example 1.

Alkali resistance

These mortars were immersed in 5M NaOH solution for 30 days. After 30 days, Mortar 1 degraded more significantly than Mortar 2 and Mortar 2 degraded more significantly than Mortar 3.

The compressive strength of the mortar cylinders was determined using a tension-controlled Zwick Z100 tensile machine with a 100 kN load cell. The compressive strengths of three different mortars before and after soaking in 5M NaOH are given in Table 2.

Table 2. Compressive strength of sulfur mortar after immersion in 5M NaOH

mortar sulfur   Compressive strength (MPa) start After 30 days in 5M NaOH 1 Unmodified 60 7 2 Modified with 11wt% STX ^TM 58 34 3 Modified with 2.5 wt% ENB 69 51

Example 3

The stability of the three different modified sulfurs to the allotropic transition was compared by wide angle X-ray spectroscopy (WAXS). Modified sulfur was prepared by heating elemental sulfur and a modifier in an amount of 5 wt % based on the weight of sulfur at 140° C. for 1 hour. The mixture was then poured into aluminum molds and allowed to set at room temperature. The crystal structure of the resulting sample (1.5 x 1 x 1 cm) was analyzed by WAXS during 650 hours after 30 minutes from the pouring of the mixture into the mold. Add the following amount of modifier to the sulfur:

Sulfur sample 10: 5.0 wt% of 5-ethylidene-2-norbornene (according to the invention).

Sulfur sample 11: 5.0 wt% of STX ^™ (not according to the invention).

Sulfur sample 12: 5.0 wt% Chempruf modifier (not according to the invention). Sample 12 was prepared by heating sulfur and a commercially available modifier concentrate (Chempruf CONCENTRATE; from GRC Inc., Clarksville, TN) in an amount of 5 wt% based on the total sulfur weight. Chempruf CONCENTRATE includes 25wt% modifier and 75wt% sulfur.

X-ray diffraction measurements show that the sulfur in sample 10 has stable monoclinic crystals. Even after 650 hours, the monoclinic crystals (beta crystallinity) did not transform into the orthorhombic crystal form (alpha crystallinity). In Examples 11 and 12, a crystal transition from monoclinic to orthorhombic was observed.

Example 4

The binder-aggregate bond of Mortars 1, 2 and 3 (see Example 2) was determined by Environmental Scanning Electron Microscopy (ESEM) using a Philips XL30 FEG-ESEM in high vacuum mode. For the ESEM analysis, the mortar was typically broken up by hand until fragments of about 1 x 1 x 1 cm were obtained. The part of the surface to be inspected is covered with a carbon layer.

ESEM analysis showed that in mortar 1 (with unmodified sulfur as a binder), the bond between sand and sulfur was worse than in the two mortars using modified sulfur as a binder. The ESEM analysis also showed that the unmodified sulfur in Mortar 1 was more brittle than the modified sulfur in Mortars 2 and 3. In Mortar 1, there was significant cracking in the sulfur phase itself. Sulfur modified with 2.5 wt% 5-ethylidene-2-norbornene (in mortar 3) was less friable than STX ^™ modified sulfur in mortar 2 (with some cracking in the sulfur phase itself) ( There is virtually no cracking in the sulfur phase itself).

Claims (13)

1. Modified sulfur prepared by mixing molten elemental sulfur with one or more olefinic sulfur modifiers, wherein at least 50% by weight of said olefinic sulfur modifier is 5-ethylene-2-nor Bornene and/or 5-vinyl-2-norbornene, wherein the total amount of olefinic sulfur modifier is 0.1-20 wt%, based on the weight of sulfur. 2. The modified sulfur of claim 1, wherein at least 80 wt% of said olefinic sulfur modifier is 5-ethylidene-2-norbornene and/or 5-vinyl-2-norbornene. 3. The modified sulfur of claim 1 or 2, wherein no olefinic sulfur modifier other than 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene is combined with said elemental sulfur mix. 4. The modified sulfur of claim 3, wherein no olefinic sulfur modifier other than 5-ethylidene-2-norbornene is admixed with said elemental sulfur. 5. Modified sulfur according to any one of the preceding claims, wherein the total amount of olefinic sulfur modifier is 5-15 wt%, preferably 7-12 wt%, based on the weight of sulphur. 6. The modified sulfur of any one of claims 1-4, wherein the total amount of olefinic sulfur modifier is 0.1-5 wt%, based on the weight of sulfur. 7. A product comprising modified sulfur as a binder, prepared by mixing the modified sulfur of any one of the preceding claims, fillers and/or aggregates, and any Selected elemental sulfur, and solidifying the resulting mixture by cooling the mixture to a temperature below the melting temperature of sulfur. 8. The product of claim 7, wherein the amount of olefinic sulfur modifier mixed in the preparation of said modified sulfur is at most 5 wt% of the total weight of sulfur in said product. 9. The product of claim 7 or 8, wherein the product is sulfur cement or a sulfur cement-aggregate composite. 10. The product according to any one of claims 7-9, prepared by mixing modified sulfur according to claim 5, elemental sulfur and fillers and/or aggregates. 11. The product according to any one of claims 7-9, prepared by mixing the modified sulfur according to claim 6 with fillers and/or aggregates. 12. The product of any one of claims 8-11, wherein the amount of the olefinic sulfur modifier mixed in the preparation of the modified sulfur accounts for 0.1-4.0 wt% of the total weight of sulfur in the product , preferably 0.1-3.0 wt%. 13. The product of any one of claims 7-12, wherein the amount of olefinic sulfur modifier other than 5-ethylidene-2-norbornene or 5-vinyl-2-norbornene is at most 1% by weight of the total weight of sulfur in the product.